Optical heads for imaging emit a plurality of light spots on a light-sensitive medium, the optical imaging head may be configured from an array of pigtailed laser diodes. Each laser diode is optically coupled to a proximal tip of a multi-mode optical fiber. The distal tips of the optical fibers are supported in a linear array by opto mechanical means, and imaged onto a printing plate.
Different types of plates may be used in CTP machines. For example, for direct engraving of a flexography plate high power lasers are used. To achieve a good ablation of the imaging media, the optical head should be provided with features such as autofocus, thermal lens compensating and plate sensitivity sensor.
Such features become feasible by the present invention which offers a confocal fiber optic sensor configured to operate within the imaging heads of CTP machines.
The confocal technique is well known in the literature. The fundamental principles and advantages of confocal microscopy are described in U.S. Pat. No. 3,013,467 (Minsky et al.).
U.S. Pat. Nos. 6,310,710 and 6,466,352 describe a rotating reading and writing scan system that incorporates a rotatable confocal microscopy. The rotatable configuration is the essence of those inventions, which also utilize the well known confocal microscopy. The novelty of these patents is in the new rotatable configuration. The present invention addresses different features in the realm of CTP devices, and more specifically in the field of three dimensional direct engraving of flexographic plates. The application utilizes the confocal principle as well, but beyond that it also offers new configurations which are adapted to achieve numerous features required for CTP devices.